(typical of long bones): formation preceded by cartilaginous analge (mesenchymal) which is dissolved then removed by osteoclasts, allowing for the in growth of blood vessels and osteoprogenitor cells.

Primary center of ossification

: the periostium produces osteoprogenitor differentiation into oseoblasts that deposit the cortex of the midshaft of long bone.

Secondary center of ossification:

the expansion of primary ossification creates 2 centers of endochondral ossification in both epiphysis of long bones: the secondary centers of ossification

Growth Plate

: the plate of cartilage that becomes trapped between the 2 centers of ossification.

generates cancelous bone and elongation of long bone.

Intramembranous

: (typical of flat bones) : bone formation directly from a fibrous layer of tissue that was derived from mesenchyme. In more mature bone, this also takes place along the periostium of the diaphysis of long bone.

Gross and Hystopathologic Structures:

Epiphysis

Epiphyseal plate = growth plate

Diaphysis

Metaphysis: zone of endochondral ossification

Periosteum: important in the appositional (layering) growth and repair medullary cavity

Endostium: has a higher level of remodeling than the periostium and is important in bone turnover